Fix exit code with bogus command name

Running this:

$ kolla-ansible bogus-command

Should show usage & give a non-zero exit code. Previously it gave a zero
exit code. This change fixes the issue.

Closes-Bug: #1929397

Change-Id: I580c208d61d5efe115f936dfb8f3f6508acd91b2

releasenotes/notes/cli-exit-code-1e6278f803dbf8e2.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixes an issue where ``kolla-ansible`` exits with a zero exit code when
+    executed with a bogus command name. `LP#1929397
+    <https://bugs.launchpad.net/kolla-ansible/+bug/1929397>`__

tools/kolla-ansible

@@ -471,7 +471,7 @@ EOF
         exit 0
         ;;
 (*)     usage
-        exit 0
+        exit 3
         ;;
 esac